U.S. Pat. No. 4,237,238 describes improved polyisocyanurate foam obtained by bringing together in the presence of a blowing agent and trimerization catalyst an organic polyisocyanate and a polyol mixture prepared by the transesterification, with a glycol of molecular weight from about 60 to about 400, of a residue obtained from the manufacture of dimethyl terephthalate. Polyol mixtures of this type are described in greater detail in U.S. Pat. No. 3,647,759 and are available commercially from Hercules, Inc., Wilmington, Del. under the tradename Terate.RTM. Resins.
The foams described in U.S. Pat. No. 4,237,238 are said to be characterized by a high degree of fire resistance with low smoke evolution on combustion and low foam friability. Unfortunately, polyols of the type described in the U.S. Pat. No. 4,237,238 patent have poor compatibility with the fluorocarbon blowing agents, especially monofluorotrichloromethane, which are generally preferred in the industry for use in making rigid polyurethane and polyisocyanurate foams. To deal successfully with this poor compatibility it has frequently been necessary to introduce the blowing agent by separate stream (which is relatively inefficient since it allows blowing agent to at least partially separate prior to foaming) or to mix polyols of the type described above with other polyols to improve the overall compatibility of the polyol mixture with the blowing agent. It has also been indicated in the literature that methoxylated nonylphenyl surfactant is effective in improving compatibility between fluorocarbon blowing agents and polyols of the type described above (journal of cellular plastics May/June 1980 page 152-158). There is, however, a need for more effective improvement in compatibility than is afforded by such nonylphenyl surfactants.
U.S. Pat. No. 4,339,343 discloses miscible blends of 20-85% alkoxylated alkyl amines with 15-80% primary hydroxyl polyols and fluorocarbon blowing agent, but does not contemplate the use of the special type of polyols described in U.S. Pat. Nos. 4,237,238 and 3,647,759.